Improvement in countersinks



UNITED STATES PATENT OFFICE.

SAMUEL ELLIOT noLEnoox, JE., 0E VcHAELESTowN7 MASSACHUSETTS.

IMPROVEMENT IN couNTERslNKs.

Specification forming part of Letters Patent No. 103,461, dated May 24,1870.

To all whom it may concern: Beit known that I, SAMUEL ELLIOT HOL- BRooK, Jr., of the city of Charlestown, in the county ot Middlesexand State of Massachusetts, have invented a new' and Improved Countersink-Gimlet; and I do hereby declare that the following is afull and exact description of aperture for the insertion of plugs.; or, by reversal of my tool or device, I convert the same into a stop, to prevent the too great penetra tion of the gimlet or auger.

1nl the drawings annexed, Figure 1 is a view of my device from one Side. Fig. 2 is a view of the same from a sideat right angles to the first named; and

In the drawings, A, Figs. 1 and 2, is my gimlet, for which I sometimes `slbstitute an auger. This gimlet is made in the usual shape of gimlets, and` needs no further description, as I claim nothing in the peculiar construction ofthe gimlet." B, Figs. 1 and 2, is my reaming device, the object of whose use is the enlargement of the top of a bored hole so as' to admit ofthe insertion of the top of a screw, and leaving the upper surface of the same iiush with the surface of thebored plank or other substance into which the gimlet makes a hole. My reamer -is thus made: It is a short tube, BX,

Figs. 1 yand 2,-fastened, when in use, to the shaft of the gimlet, by a thumb-screw, C, Figs. 1 and 2, or aset-screw, which tube bears above (and firmly attached to it, being cast in the vsame piece) a truncated cone, D, Figs. 1 and 2, bored through its center, so as to admit the passage of the gimlet (oranger) shaft. This cone isvcut away in an axial line, (see Fig. 2,) so that but half of it is left-the edge seen in Fig. 2, and on the left hand in Fig. 1, being the the cutting-edge. I cut away or chamfer this cutting-edge in any convenient manner. I use this device, also, in another way'. Withdrawing it from the gimlet-shaft, I reverse it, and, replacing and fastening it again, by means ofthe thumb-screw C, it answers as a stop, to

prevent the too great penetration of my gimlet or auger.

Where many holes are to be bored, as in the building of Ships, &c., the advantages of the use ot' this device are too obvious to need further enlarging upon. I

l The next portion of my invention is theeonntersinking portion, which gives the name to my device. D, Figs. 1 and 2, is my countersinking device, composed o f a thick cylinder of metal, D", Figs. 1 and 2, bored through the center, so as to admi-t of the passage of the gimlet-shaft, and secured to it, like my reaming device, by a thumb or set screw, E, Figs. 1 and 2. From one end of this cylinder D7 (the lower end, as seen in the drawing,) proceeds a plate of steel or other metal, F, Fig.V

2, F Gr, Fig. 1, which, on one side, at F, Fig. 1, of the gimlet-shaft, is fashioned, at its lower end, into a cutter, whose use is to remove, byV horizontal cutting, a ring of wood surroundin g the bored aperture, and at the other -side G, Fig. 1, is so fashioned as that, at the farthest point from the center of the,fgimletshaft, a sharp point-projects downward, whose use is to inscribe the inci'sed circle which describes the periphery of theproposed enlargement of the bored aperture.

And the operation of my device is this: When I propose to bore a hole in a plank, and reain the top of the same, so as to admit of the sinking of the head of a screw, I place the device B and G on the gimlet, and fasten it by' the thumb or set screw C. Having bored the'hole 'in the usual manner, I continue the boring ac.

tion till the cutting-edge of my reamer has cut the conical aperture made by itto a sniiicient depth, when the operation is nished.

To bore a hole to a certain depth, I withdraw, reverse, replace, and refasten my reaming device B and C at any distance desired from the point ofthe gimlet, when, the pointoflthe gimlet having penetrated to the desired distance, the farther penetration is automatically stopped. My countersinking device is susceptible, by reversion, of ihe same use.

To countersink, I place myicountersinking arrangement D and C in the position occupied vin the drawing by the reamerB, reversing it so that the cutting parts are toward the gimlet-point, and operate in the same manner as hereinbefore explained as to the reamer, cntting to any depth desirable, according to the thickness which I Want my plug to be.' v

I do not confine myself to any particular bevel of my reamer, or to any peculiar fashion of the cutting' portion of it, or of the counter.

As a new article of manufacture, the adjust able reamer A and countersillk D, both constructed as described, and arranged in combination with a bit or gimlet7 to operate as and for thc purpose described.

SAMUEL ELLIOT .HOLBROOK7 JR.

Witnesses LMUEL P. JENKS, A. J. YOUNG. 

